Electric motors are widely used to drive mechanical systems in industrial applications. A motor system usually includes a controller for controlling operation of the electric motor. The controller adjusts the operation, such as speed, torque, and power, of the electric motor based on many control parameters. In many applications, it is desired to operate the electric motor to provide constant output power in a variety of operational conditions.
U.S. Pat. No. 5,123,080 discloses a constant torque electric motor for driving an air conditioner compressor. The motor receives a power frequency and a power voltage as inputs and provides a constant torque within a frequency range of 6 to 60 Hz. From 60 Hz to 90 Hz, the power voltage input to the constant torque motor is constant at 230 V, resulting in the motor producing a constant horsepower output over this power frequency range. By varying the power frequency and the power voltage simultaneously, the motor speed becomes controllable resulting in the control of the air conditioner compressor and corresponding cooling capability of the system.
In conventional, electric motor control systems, however, there are problems that adjustments of motor operations are inflexible. In addition, it is difficult to maintain output power of an electric motor when a rotational speed of the electric motor varies significantly. The system of the present disclosure is directed to improving upon existing technologies.